Magnetic Device and Power Converter Employing the Same

ABSTRACT

A magnetic device and power converter employing the same. In one embodiment, the magnetic device includes a first L-core segment including a first leg and a second leg extending therefrom, and an opposing second L-core segment including a first leg and a second leg extending therefrom. The magnetic device also includes a winding formed around at least one of the first leg and the second leg of the first L-core segment or the second L-core segment.

TECHNICAL FIELD

The present invention is directed, in general, to power electronics and, more specifically, to a magnetic device and power converter employing the same.

BACKGROUND

A switched-mode power converter (also referred to as a “power converter” or “regulator”) is a power supply or power processing circuit that converts an input voltage waveform into a specified output voltage waveform. Magnetic devices such as transformers and inductors are often employed in power converters to store and/or transfer electrical energy through the power converter. Inasmuch as the magnetic devices tend to account for a fair amount of the board space of the power converter and take up disproportional time of the manufacturing process, it is advantageous to employ a compact magnetic device with flexible design. Therefore, what is needed in the art is a building block for a less complex magnetic core amenable to compact magnetic devices.

SUMMARY OF THE INVENTION

Technical advantages are generally achieved, by advantageous embodiments of the present invention, including a magnetic device and power converter employing the same. In one embodiment, the magnetic device includes a first L-core segment including a first leg and a second leg extending therefrom, and an opposing second L-core segment including a first leg and a second leg extending therefrom. The magnetic device also includes a winding formed around at least one of the first leg and the second leg of the first L-core segment or the second L-core segment.

The foregoing has outlined rather broadly the features and technical advantages of the present invention in order that the detailed description of the invention that follows may be better understood. Additional features and advantages of the invention will be described hereinafter, which form the subject of the claims of the invention. It should be appreciated by those skilled in the art that the conception and specific embodiment disclosed may be readily utilized as a basis for modifying or designing other structures or processes for carrying out the same purposes of the present invention. It should also be realized by those skilled in the art that such equivalent constructions do not depart from the spirit and scope of the invention as set forth in the appended claims.

BRIEF DESCRIPTION OF THE DRAWINGS

For a more complete understanding of the present invention, reference is now made to the following descriptions taken in conjunction with the accompanying drawings, in which:

FIG. 1 illustrates a block diagram of an embodiment of a power converter;

FIGS. 2 and 3 illustrate schematic diagrams of exemplary power trains of a power converter employing a boost regulator;

FIGS. 4 and 5 illustrate schematic diagrams of embodiments of portions of power converters;

FIG. 6 illustrates a timing diagram demonstrating an operation of the power converter of FIGS. 4 and 5;

FIGS. 7 and 8 illustrate schematic diagrams of alternative embodiments of portions of power converters;

FIG. 9 illustrates a schematic diagram of an alternative embodiment of a power converter;

FIG. 10 illustrates a schematic diagram of an alternative embodiment of a power converter;

FIG. 11 illustrates perspective view of an embodiment of a portion of a magnetic device;

FIG. 12 illustrates a side view of an embodiment of a portion of a magnetic device; and

FIGS. 13 to 49 illustrate views of embodiments of magnetic devices.

Corresponding numerals and symbols in the different figures generally refer to corresponding parts unless otherwise indicated, and may not be redescribed in the interest of brevity after the first instance. The FIGUREs are drawn to illustrate the relevant aspects of exemplary embodiments.

DETAILED DESCRIPTION OF ILLUSTRATIVE EMBODIMENTS

The making and using of the present exemplary embodiments are discussed in detail below. It should be appreciated, however, that the present invention provides many applicable inventive concepts that can be embodied in a wide variety of specific contexts. The specific embodiments discussed are merely illustrative of specific ways to make and use the invention, and do not limit the scope of the invention.

The present invention will be described with respect to exemplary embodiments in a specific context, namely, magnetic devices employing an L-shaped core, methods of forming the same and power converters employing the magnetic devices. While the principles of the present invention will be described in the environment of a power converter, any application that may benefit from the magnetic devices as described herein including a power amplifier or a motor controller is well within the broad scope of the present invention.

Referring initially to FIG. 1, illustrated is a block diagram of an embodiment of a power converter. The power converter is coupled to a source of electrical power such as an ac mains for providing an ac input voltage V_(in). The power converter includes a power train 105 that is controlled by a controller 110. The controller 110 generally measures an operating characteristic of the power converter such as an output voltage V_(out) and controls a duty cycle (generally designated “D”) of a switch therein in response to the measured operating characteristic to regulate the characteristic. The power converter may form a section of a power supply and provide power to another subsystem thereof, such as an isolating dc-to-dc converter coupled to an output thereof that provides a regulated voltage to a load. The power train 105 may employ a regulator (e.g., a boost or buck regulator) as described herein. The power train 105 of the power converter generally includes a plurality of switches coupled to reactive circuit elements to provide the power conversion function.

Turning now to FIGS. 2 and 3, illustrated are schematic diagrams of exemplary power trains of a power converter employing a boost regulator. Beginning with FIG. 2, illustrated is a power train 200 employing a boost regulator. The power converter receives an input voltage V_(in), (e.g., an unregulated ac input voltage) from a source of electrical power such as an ac mains at an input thereof and provides a regulated output voltage V_(out) at an output of the power converter. In keeping with the principles of a boost topology, the output voltage V_(out) is generally higher than the input voltage V_(in), such that a switching operation thereof can regulate the output voltage V_(out). A main switch S₁(e.g., an N-channel metal-oxide semiconductor “active” switch) of the boost regulator is enabled to conduct by a gate drive signal GD for a primary interval D and couples the input voltage V_(in), through a rectifier bridge 205 to a boost inductor L_(boost). During the primary interval D, a rectified input current or input current flows through the boost inductor L_(boost) to local circuit ground.

The duty cycle for the power train 200 depends in steady state, under continuous current in the boost inductor L_(boost), on the ratio of the input and output voltages V_(in), V_(out), respectively, according to the equation:

$D = {1 - {\frac{V_{in}}{V_{out}}.}}$

During a complementary interval 1-D, the main switch S₁ is transitioned to a non-conducting state and an auxiliary switch (e.g., a diode D1) conducts. In an alternative circuit arrangement, the auxiliary switch may include a second active switch that is controlled to conduct by a complementary gate drive signal. The diode D1 provides a path to maintain continuity of the input current i_(in) flowing through the boost inductor L_(boost). During the complementary interval 1-D, the input current i_(in) flowing through the boost inductor L_(boost) decreases, and may become zero and remain zero for a period of time resulting in a “discontinuous conduction mode” of operation.

During the complementary interval 1-D, the current flowing through the boost inductor L_(boost) flows through the diode D1 into an output filter capacitor C. In general, the duty cycle of the main switch S₁ (and the complementary duty cycle of the diode D1) may be adjusted to maintain a regulation of the output voltage V_(out) of the power converter. The conduction periods for the main and auxiliary switches may be substantially equal or varied to maintain a regulation of the output voltage V_(out) of the power converter. Those skilled in the art understand that conduction periods for the main and auxiliary switches may be separated by a small time interval by the use of “snubber” circuit elements (not shown) or by control circuit timing to avoid cross conduction current therebetween, and beneficially to reduce the switching losses associated with the power converter. Circuit and control techniques to avoid cross conduction currents between switches are well understood in the art and will not be described further in the interest of brevity.

Turning now to FIG. 3, illustrated is an exemplary power train 300 of a power converter employing first and second boost regulators coupled to first and second boost inductors L_(boost1), L_(boost2), respectively. The first boost regulator includes a first main switch S1 and a first auxiliary switch (e.g., a first diode D1). The second boost regulator includes a second main switch S2 and a second auxiliary switch (e.g., a second diode D2). The first and second main switches S1, S2 receive first and second gate drive signals GD_(S1), GD_(S2), respectively, generally controlled to operate roughly 180 degrees out of phase with respect to each other. Out-of-phase operation of the boost regulators provides an interleaving effect that doubles the ripple frequency and reduces the ripple magnitude for an ac input current delivered to a rectifier bridge 305. The rectifier bridge 305 provides a rectified input current or input current i_(in). A similar effect is achieved for the current supplied to an output filter capacitor C. The reduction of switching ripple in the ac input current helps reduce filtering requirements for an input filter (not shown) to reduce undesirable high-frequency components. Although substantial benefits can accrue from the interleaving effects between two boost regulators, the design challenges previously described to implement efficient boost inductors still remain. Remaining circuit elements in FIG. 3 and in following FIGUREs that are similar to those in FIG. 2 and other FIGUREs will not generally be described again in the interest of brevity.

Turning now to FIGS. 4 and 5, illustrated are schematic diagrams of embodiments of portions of power converters. More specifically, FIG. 4 illustrates a power train employing a boost topology with two interleaved boost regulators (e.g., first and second boost regulators) and a coupled boost inductor L_(boost). It should be understood, however, that other topologies such as a buck topology with interleaved regulators (e.g., first and second regulators) and a coupled inductor as described herein are well within the broad scope of the present invention. The coupled boost inductor L_(boost) includes a common winding N_(ic) (coupled between nodes 1 and 2), a first winding N_(sc1) (coupled between nodes 2 and 3), and a second winding N_(sc2) (coupled between nodes 2 and 4). The first and second windings N_(sc1), N_(sc2) are electrically and magnetically coupled to the common winding N_(ic). In an advantageous embodiment, the first and second windings N_(sc1), N_(sc2) have equal numbers of turns and will hereinafter be represented with a reference symbol N_(S). Dots are illustrated in the FIGURE adjacent to the windings to indicate the sense of each winding (i.e., the winding direction and the sense of the magnetically induced voltage therein).

In an advantageous embodiment, the interleaved boost regulators are controlled to provide an input current with high-power factor. The first boost regulator includes a first main switch (e.g., a field-effect transistor) S₁ and a first auxiliary switch (e.g., a first diode D1), and is coupled to a portion of the coupled boost inductor L_(boost) including the common winding N_(ic) and the first winding N_(ic1). The second boost regulator includes a second main switch (e.g., a field-effect transistor) S₂ and a second auxiliary switch (e.g., a second diode D2), and is coupled to a portion of the coupled boost inductor L_(boost) including the common winding N_(ic) and the second winding N_(sc2). The output currents from the boost regulators of the power train are interleaved and flow through the first and second diodes D1, D2 into an output filter capacitor C. Similarly, the rectified input current or input current i_(in) to the boost regulators are interleaved and flow through the common winding N_(ic). The first and second main switches S₁, S₂ are controlled by control signals GD_(s1), GD_(s2), respectively, to provide duty-cycle control for each of the two interleaved boost regulators. Typically, the control signals GD_(si), GD_(s2) are controlled 180 degrees out of phase with respect to each other, and provide a common duty cycle (generally designated “D”) for each boost regulator. It is also possible for the control signals GD_(s1), GD_(s2) to be independently controlled to provide two distinct duty cycles to ensure that the inductor currents i₁, i₂ are equal. A load, represented by current source CS, is coupled to output terminals of the power converter and draws a current i_(o).

A common winding N_(ic) with selected turns can be formed around a common leg (e.g., a center leg) of a magnetic core of the coupled boost inductor L_(boost). In an alternative embodiment, the common winding N_(ic) with selected turns may be formed around a common leg of a magnetic core that is not geometrically a center leg. Thus, the term common leg may include a leg of a magnetic core that may not be geometrically located as a center leg. (See, e.g., U.S. Pat. No. 8,125,205, entitled “Power Converter Employing Regulators with a Coupled Inductor,” issued on Feb. 28, 2012, to Chandrasekaran, et al., which is incorporated herein by reference.)

With respect to FIG. 5, illustrated is a schematic diagram of an alternative embodiment of a power converter with a power train having two interleaved boost regulators utilizing a couple boost inductor L_(boost). Again, other topologies such as a buck-boost topology with interleaved regulators (e.g., first and second regulators) and a coupled inductor as described herein are well within the broad scope of the present invention. The couple boost inductor L_(boost) includes a common winding N_(ic) between nodes 1A and 1B, coupled to node 2 thereof in a return leg of the boost regulator that is coupled to the source of electrical power for providing an input voltage V_(in). A first winding N_(sc1) of the couple boost inductor L_(boost) is coupled between nodes 2 and 3, and a second winding N_(sc2) is coupled between node 2 and node 4. The first and second windings N_(sc1), N_(cs2) are magnetically coupled to the common winding N_(ic) and are electrically coupled to the common winding N_(ic). The operation of the power converter illustrated in FIGS. 4 and 5 is substantially similar. Remaining elements in FIG. 5 with reference designations corresponding to those in FIG. 4 are substantially the same and will not be redescribed in the interest of brevity.

In a further alternative embodiment of the couple boost inductor L_(boost), the first and second windings N_(sc1), N_(sc2) can be electrically coupled together external to the magnetic device forming a portion of the couple boost inductor L_(boost). In a further alternative embodiment of the couple boost inductor L_(boost), the common winding N_(ic) can be separated into two winding parts, each part coupled in the power converter as indicated in FIGS. 4 and 5 for the respective winding.

Turning now to FIG. 6, illustrated is a timing diagram demonstrating an operation of the power converter of FIGS. 4 and 5. The period of a switching cycle is represented by the variable T_(S). The periods when the first and second main switches S₁, S₂ are enabled to conduct are represented by the quantity D T_(s), which is assumed to be the same interval of time therefor. The first and second main switches S₁, S₂ are operated 180 degrees out of phase by a delay 0.5·T_(S) as shown in FIG. 6.

Turning now to FIGS. 7 and 8, illustrated are schematic diagrams of alternative embodiments of portions of power converters. More specifically, FIG. 7 illustrates a power converter employing buck regulators with a coupled inductor. FIG. 8 illustrates a power converter employing buck-boost regulators with a coupled inductor. While the operation of the power converters of FIGS. 7 and 8 differs to accommodate the buck and buck-boost operation, respectively, the principles of the present invention with respect to the interleaved regulators and coupled inductor are analogous to the principles as described above and will not hereinafter be repeated.

Turning now to FIG. 9, illustrated is a schematic diagram of an alternative embodiment of a power converter. The power converter includes two interleaved half-bridge, isolated current double rectifiers (designated “CDR-I” and “CDR-II”). The power converter is operated by applying an ac input voltage through a source of electrical power through a bridge rectifier (not shown) to provide a dc input voltage V_(dc) to respective primary windings. The dc input voltage V_(dc) is connected across a first series-connected pair of switches S₁₁, S₁₂, and across a second series-connected pair of switches S₂₁, S₂₂. The first series-connected pair of switches S₁₁, S₁₂ are connected together at a first node N₁, and the second series-connected pair of switches S₂₁, 5 ₂₂ are connected together at a second node N₂. The first and second series-connected pair of switches S₁₁, 5 ₁₂, 5 ₂₁, 5 ₂₂ are preferably field-effect transistors, each having a parasitic diode connected thereacross. The dc input voltage V_(dc) is also connected across a pair of capacitors C1, C2, which are connected together at a first common node N_(c1). The first and second series-connected pair of switches S₁₁, S₁₂, S₂₁, S₂₂ are operated with a controller 910 to generate a first drive voltage V_(p1) between the first node N₁ and the first common node N_(ci), and a second drive voltage V_(p2) between the second node N₂ and the first common node N_(c1).

The first interleaved half-bridge, isolated current double rectifier CDR-I includes two series-connected primary windings PR₁₁, PR₁₂, which are connected across the first node N₁ and the first common node N_(c1) and thus are driven with the first drive voltage V_(p1). A pair of secondary windings SC₁₁, SC₁₂ are connected together at an output node N_(o), and are magnetically coupled to the primary windings PR₁₁, PR₁₂, respectively. A pair of series-connected synchronous rectifier switches SR₁₁, SR₁₂ are connected in parallel with secondary windings SC₁₁, SC₁₂, respectively, and connected together at a second common node N_(c2). Similarly, the second interleaved half-bridge, isolated current double rectifier CDR-II includes two series-connected primary windings PR₂₁, PR₂₂, which are connected across the second node N₂ and the first common node N_(c1) and thus are driven with the second drive voltage V_(p2). A pair of secondary windings SC₂₁, SC₂₂ are connected together at an output node N_(o), and are magnetically coupled to the primary windings PR₂₁, PR₂₂, respectively. A pair of series-connected synchronous rectifier switches SR₂₁, SR₂₂ are connected in parallel with secondary windings SC₂₁, SC₂₂, respectively, and connected together at the second common node N_(c2). The synchronous rectifier switches SR₁₁, SR₁₂, SR₂₁, SR₂₂ are preferably field-effect transistors, each having a parasitic diode connected thereacross. Alternatively, the synchronous rectifier switches SR₁₁, SR₁₂, SR₂₁, SR₂₂ can be replaced with diodes and oriented in a similar manner to the parasitic diodes. An output filter capacitor C3 is connected between the output node N_(o) and the second common node N_(c2), wherein an output voltage V_(o) is to be provided to a load coupled thereto.

The ac input voltages are generated in accordance with the symmetric modulation scheme. In accordance therewith, the drive voltages applied to respective current doubler rectifiers are phase-shifted with respect to each other by T_(s)/(2*N), wherein T_(s) is the drive voltages' switching period and N is the number of current doubler rectifiers. For the illustrated power converter with N=2, the controller 910 operates the switches S₁₁, S₁₂, S₂₁, S₂₂ such that the first and second drive voltages V_(p1), V_(p2) are phase-shifted by one-fourth the switching period T_(s), which ensures that the rectified output currents of the two current doubler rectifiers are interleaved. The controller 910 also provides the signals needed to operate the synchronous rectifier switches SR₁₁, SR₁₂, SR₂₁, SR₂₂. The controller 910 operates the aforementioned switches in accordance with the output voltage V_(o) of the power converter. (See, e.g., U.S. Pat. No. 7,046,523, entitled “Core Structure and Interleaved DC-DC Converter Topology,” issued on May 16, 2006, to Sun, et al. and U.S. Pat. No. 8,134,443, entitled “Extended E Matrix Integrated Magnetic (MIM) Core,” issued on Mar. 13, 2012, to Chandrasekaran, et al., which are incorporated herein by reference.)

Turning now to FIG. 10, illustrated is a schematic diagram of an alternative embodiment of a power converter. The power converter includes a current doubler rectifier (“CDR”) and a controller. The current doubler rectifier employs a double-ended, half-bridge topology which is capable of applying positive, negative, and zero voltages thereacross. The current doubler rectifier includes first and second capacitors C1, C2, and first and second switches S₁, S₂. The first and second capacitors C1, C2 and the first and second switches S₁, S₂ receive a dc input voltage V_(in). The first and second capacitors C1, C2 may, for example, be electrolytic tantalum capacitors and the first and second switches S₁, S₂ may be metal-oxide semiconductor field-effect transistors.

The current doubler rectifier includes a magnetic device with a magnetic core MC, a primary winding (designated “N_(p)”) and a secondary winding (designated “N_(s)”). The current doubler rectifier also includes an output filter capacitor C_(out), and first and second rectifier diodes D₁, D₂. The magnetic core MC includes a center leg CL, a first outer leg OL1 and a second outer leg OL2. The first and second outer legs OL1, OL2 are disposed on opposite sides of the center leg CL. The primary winding N_(p) includes a first primary winding PR1 that is formed around the first outer leg OL1 and a second primary winding PR2 formed around the second outer leg OL2. The secondary winding N_(s) includes first, second and third secondary winding SC1, SC2, SC3 formed around the first outer leg OL1, the second outer leg OL2 and the center leg CL, respectively. The duty cycle of the first and second switches S₁, S₂ is controlled so as to reduce a deviation of an output voltage V_(o) from a predetermined setpoint level.

In addition to controlling the duty cycle of the first and second switches S₁, S₂, a controller may also control the output rectifiers when the first and second rectifier diodes D₁, D₂ are replaced with active switches (e.g., synchronous rectifier switches). The controller includes an isolation circuit (e.g., a transformer) that provides electrical isolation between the components on either side of the magnetic device.

In operation, the input voltage V_(in), is applied to the first and second capacitors C1, C2 and the first and second switches S₁, S₂. The first and second switches S₁, S₂ are controlled by a drive control circuit of the controller in a complementary way. The first and second switches S₁, S₂ apply an ac voltage V_(ab) to the primary winding N_(p) leading to a first current i₁ through the first secondary winding SC1, a second current i₂ through the second secondary winding SC2 and a third current i₃ through the third secondary winding SC3 (where i₁+i₂=i₃). The first and second currents i₁, i₂ are rectified by the first and second rectifier diodes D₁, D₂, respectively. The third current i₃ charges the output filter capacitor C_(out), which then provides power to a load coupled to the output of the power converter. (See, e.g., U.S. Pat. No. 6,549,436, entitled “Integrated Magnetic Converter Circuit and Method with Improved Filtering,” issued on Apr. 15, 2003, to Sun, which is incorporated herein by reference.)

Turning now to FIG. 11, illustrated is perspective view of an embodiment of a portion of a magnetic device. In particular, an L-core segment is illustrated having a first leg LEG1 and a second leg LEG2. The first leg LEG1 has a length L1 and a thickness TH1 and the second leg LEG2 has a length L2 and a thickness TH2. In an illustrated embodiment, the length L1 of the first leg LEG1 is elongated (i.e., extended or longer) with respect to the length L2 of the second leg LEG2 (e.g., L1≠L2) and the second leg LEG2 is substantially perpendicular to the first leg LEG1. It should be understood, however, that the first and second legs LEG1, LEG2 may be substantially the same length (e.g., L1=L2) and the second leg LEG2 may extend from the first leg LEG1 at different angles. While the first and second legs LEG1, LEG2 are illustrated having the same thickness (e.g., TH1=TH2), it is contemplated that the thickness of the legs may be different (e.g., TH1≠TH2). The L-core segment provides a less complex magnetic core amenable to compact magnetic devices. The L-core segment also provides a structure that allows windings to be formed thereabout without a bobbin. Additionally, the L-core segment can be used as a building block for multiple magnetic core geometries and magnetic device assemblies.

Turning now to FIG. 12, illustrated is a side view of an embodiment of a portion of a magnetic device. A magnetic core of the magnetic device includes a first L-core segment LC1 and an opposing second L-core segment LC2. The first L-core segment LC1 includes a first leg LEG1 and a second leg LEG2 extending therefrom. The second L-core segment LC2 includes a first leg LEG1 and a second leg LEG2 extending therefrom. An end surface ES of the second leg LEG2 of the first L-core segment LC1 mates with (e.g., glued, adhesively secured or banded together) a portion of an internal surface IS of the first leg LEG1 of the second L-core segment LC2. Also, an end surface ES of the second leg LEG2 of the second L-core segment LC2 mates with (e.g., glued, adhesively secured or banded together) a portion of an internal surface IS of the first leg LEG1 of the first L-core segment LC1. The first and second L-core segments LC1, LC2 may be designed with the flexibility as described above with respect to FIG. 11.

Turning now to FIGS. 13 to 16, illustrated are views of an embodiment of a magnetic device. FIGS. 13 and 14 illustrate a schematic view and a side view, respectively, of the magnetic device having primary windings coupled in series and secondary windings coupled in parallel around a magnetic core. FIGS. 15 and 16 illustrate partially assembled perspective views of the magnetic device. The magnetic core of the magnetic device includes a first L-core segment LC1 and an opposing second L-core segment LC2. The first L-core segment LC1 includes a first leg LEG1 and a second leg LEG2 extending therefrom. The second L-core segment LC2 includes a first leg LEG1 and a second leg LEG2 extending therefrom. The first and second L-core segments LC1, LC2 may be designed with the flexibility as described above with respect to FIGS. 11 and 12.

The magnetic device includes a first primary winding PR1 coupled in series with a second primary winding PR2 with first, second and third primary terminals p₁, p₂, p₃ for connection to another circuit element of a power converter or the like. An end of the first and second primary windings PR1, PR2 are coupled together at the third primary terminal p₃. The first primary winding PR1 is formed around (e.g., wound around) the first leg LEG1 of the first L-core segment LC1 and the second primary winding PR2 is formed around (e.g., wound around) the first leg LEG1 of the second L-core segment LC2.

The magnetic device includes a first secondary winding SC1 coupled in parallel with a second secondary winding SC2 with first and second secondary terminals s₁, s₂ for connection to another circuit element of a power converter or the like. An end of the first and second secondary windings SC1, SC2 are coupled together. The first secondary winding SC1 is formed around (e.g., stamped and formed sheet of metal placed around) the first leg LEG1 of the first L-core segment LC1 and the second secondary winding SC2 is formed around (e.g., stamped and formed sheet of metal placed around) the first leg LEG1 of the second L-core segment LC2. The first secondary winding SC1 is formed over the first primary winding PR1 around the first leg LEG1 of the first L-core segment LC1, and the second secondary winding SC2 is formed over the second primary winding PR2 around the first leg LEG1 of the second L-core segment LC2.

The primary windings PR1, PR2 may be dielectrically isolated from respective secondary windings SC1, SC2 by an insulating layer (e.g., tape or bobbin, not shown). Additionally, the primary windings PR1, PR2 and/or the secondary windings SC1, SC2 may be dielectrically isolated from the respective first and second L-core segments LC1, LC2 by an insulating layer (e.g., tape or bobbin, not shown). The magnetic device may also be encapsulated by a protective potting material such as epoxy individually or in combination with other circuit elements as part of a power converter or the like.

Turning now to FIGS. 17 to 20, illustrated are views of an embodiment of a magnetic device. FIGS. 17 and 18 illustrate a schematic view and a side view, respectively, of the magnetic device having primary windings coupled in parallel and secondary windings coupled in parallel around a magnetic core. FIGS. 19 and 20 illustrate partially assembled perspective views of the magnetic device. The magnetic core of the magnetic device includes a first L-core segment LC1 and an opposing second L-core segment LC2. The first L-core segment LC1 includes a first leg LEG1 and a second leg LEG2 extending therefrom. The second L-core segment LC2 includes a first leg LEG1 and a second leg LEG2 extending therefrom. The first and second L-core segments LC1, LC2 may be designed with the flexibility as described above with respect to FIGS. 11 and 12.

The magnetic device includes a first primary winding PR1 coupled in parallel with a second primary winding PR2 with first and second primary terminals p₁, p₂ for connection to another circuit element of a power converter or the like. Ends of the first and second primary windings PR1, PR2 are coupled together at the first and second primary terminals p₁, p₂. The first primary winding PR1 is formed around (e.g., wound around) the first leg LEG1 of the first L-core segment LC1 and the second primary winding PR2 is formed around (e.g., wound around) the first leg LEG1 of the second L-core segment LC2.

The magnetic device includes a first secondary winding SC1 coupled in parallel with a second secondary winding SC2 with first and second secondary terminals s₁, s₂ for connection to another circuit element of a power converter or the like. An end of the first and second secondary windings SC1, SC2 are coupled together. The first secondary winding SC1 is formed around (e.g., stamped and formed sheet of metal placed around) the first leg LEG1 of the first L-core segment LC1 and the second secondary winding SC2 is formed around (e.g., stamped and formed sheet of metal placed around) the first leg LEG1 of the second L-core segment LC2. The first secondary winding SC1 is formed over the first primary winding PR1 around the first leg LEG1 of the first L-core segment LC1, and the second secondary winding SC2 is formed over the second primary winding PR2 around the first leg LEG1 of the second L-core segment LC2.

The primary windings PR1, PR2 may be dielectrically isolated from respective secondary windings SC1, SC2 by an insulating layer (e.g., tape or bobbin, not shown). Additionally, the primary windings PR1, PR2 and/or the secondary windings SC1, SC2 may be dielectrically isolated from the respective first and second L-core segments LC1, LC2 by an insulating layer (e.g., tape or bobbin, not shown). The magnetic device may also be encapsulated by a protective potting material such as epoxy individually or in combination with other circuit elements as part of a power converter or the like.

Thus, a magnetic device, a method of forming the same and a power converter have been introduced herein. In one embodiment, the magnetic device includes a first L-core segment including a first leg and a second leg extending therefrom. The magnetic device also includes an opposing second L-core segment including a first leg and a second leg extending therefrom. The magnetic device further includes a winding formed around at least one of the first leg and the second leg of the first L-core segment or the second L-core segment. In one embodiment, the second leg of the first L-core segment is substantially perpendicular to the first leg of the first L-core segment and the second leg of the second L-core segment is substantially perpendicular to the first leg of the second L-core segment. Additionally, a length of the first leg of the first L-core segment is elongated with respect to a length of the second leg of the first L-core segment and a length of the first leg of the second L-core segment is elongated with respect to a length of the second leg of the second L-core segment. Additionally, a thickness of the first leg and the second leg of the first L-core segment is substantially equal and a thickness of the first leg and the second leg of the second L-core segment is substantially equal.

In one embodiment, a primary winding is formed around the first leg of the first L-core segment and a secondary winding is formed around one of the first leg of the first L-core segment and the first leg of the second L-core segment. In yet another embodiment, a first primary winding is formed around the first leg of the first L-core segment in series with a second primary winding formed around the first leg of the second L-core segment. Alternatively, a first primary winding is formed around the first leg of the first L-core segment in parallel with a second primary winding formed around the first leg of the second L-core segment. In a related embodiment, a first secondary winding is formed around the first leg of the first L-core segment in parallel with a second secondary winding formed around the first leg of the second L-core segment. Additionally, a first secondary winding is formed over a first primary winding around the first leg of the first L-core segment, and a second secondary winding is formed over a second primary winding around the first leg of the second L-core segment. The first and second secondary windings are stamped and formed sheets of metal.

Turning now to FIGS. 21 to 23, illustrated are views of an embodiment of a magnetic device. FIGS. 21 and 22 illustrate a schematic view and a side view, respectively, of the magnetic device having a primary winding and center-tapped secondary windings around a magnetic core. FIG. 23 illustrates a partially assembled perspective view of the magnetic device. The magnetic core of the magnetic device includes a first L-core segment LC1 and an opposing second L-core segment LC2. The first L-core segment LC1 includes a first leg LEG1 and a second leg LEG2 extending therefrom. The second L-core segment LC2 includes a first leg LEG1 and a second leg LEG2 extending therefrom. The first and second L-core segments LC1, LC2 may be designed with the flexibility as described above with respect to FIGS. 11 and 12.

The magnetic device includes a primary winding PR with first and second primary terminals p₁, p₂ for connection to another circuit element of a power converter or the like. The primary winding PR is formed around (e.g., wound around) the first leg LEG1 of the second L-core segment LC2. The magnetic device includes center-tapped secondary windings with a first secondary winding SC1 and a second secondary winding SC2 with first, second and third secondary terminals s₁, s₂, s₃ for connection to another circuit element of a power converter or the like. The center tap of the center-tapped secondary windings is coupled to the third secondary terminal s₃. The first and second secondary windings SC1, SC2 are formed around (e.g., stamped and formed sheet of metal placed around) the first leg LEG1 of the second L-core segment LC2. The first and second secondary windings SC1, SC2 are formed over the primary winding PR around the first leg LEG1 of the second L-core segment LC2.

The primary winding PR may be dielectrically isolated from the secondary windings SC1, SC2 by an insulating layer (e.g., tape or bobbin, not shown). Additionally, the primary winding PR and/or the secondary windings SC1, SC2 may be dielectrically isolated from the second L-core segment LC2 by an insulating layer (e.g., tape or bobbin, not shown). The magnetic device may also be encapsulated by a protective potting material such as epoxy individually or in combination with other circuit elements as part of a power converter or the like.

Turning now to FIGS. 24 to 27, illustrated are views of an embodiment of a magnetic device. FIGS. 24 and 25 illustrate a schematic view and a side view, respectively, of the magnetic device having primary windings coupled in series and center-tapped secondary windings around a magnetic core. FIGS. 26 and 27 illustrate partially assembled perspective views of the magnetic device. The magnetic core of the magnetic device includes a first L-core segment LC1 and an opposing second L-core segment LC2. The first L-core segment LC1 includes a first leg LEG1 and a second leg LEG2 extending therefrom. The second L-core segment LC2 includes a first leg LEG1 and a second leg LEG2 extending therefrom. The first and second L-core segments LC1, LC2 may be designed with the flexibility as described above with respect to FIGS. 11 and 12.

The magnetic device includes a first primary winding PR1 coupled in series with a second primary winding PR2 with first, second and third primary terminals p₁, p₂, p₃ for connection to another circuit element of a power converter or the like. An end of the first and second primary windings PR1, PR2 are coupled together at the third primary terminal p₃. The first primary winding PR1 is formed around (e.g., wound around) the first leg LEG1 of the first L-core segment LC1 and the second primary winding PR2 is formed around (e.g., wound around) the first leg LEG1 of the second L-core segment LC2.

The magnetic device includes center-tapped secondary windings with a first secondary winding SC1 and a second secondary winding SC2 with first, second and third secondary terminals s₁, s₂, s₃ for connection to another circuit element of a power converter or the like. The center tap of the center-tapped secondary windings is coupled to the third secondary terminal s₃. The first secondary winding SC1 is formed around (e.g., stamped and formed sheet of metal placed around) the first leg LEG1 of the first L-core segment LC1 and the second secondary winding SC2 is formed around (e.g., stamped and formed sheet of metal placed around) the first leg LEG1 of the second L-core segment LC2. The first secondary winding SC1 is formed over the first primary winding PR1 around the first leg LEG1 of the first L-core segment LC1, and the second secondary winding SC2 is formed over the second primary winding PR2 around the first leg LEG1 of the second L-core segment LC2.

The primary windings PR1, PR2 may be dielectrically isolated from respective secondary windings SC1, SC2 by an insulating layer (e.g., tape or bobbin, not shown). Additionally, the primary windings PR1, PR2 and/or the secondary windings SC1, SC2 may be dielectrically isolated from the respective first and second L-core segments LC1, LC2 by an insulating layer (e.g., tape or bobbin, not shown). The magnetic device may also be encapsulated by a protective potting material such as epoxy individually or in combination with other circuit elements as part of a power converter or the like.

Turning now to FIGS. 28 to 31, illustrated are views of an embodiment of a magnetic device. FIGS. 28 and 29 illustrate a schematic view and a side view, respectively, of the magnetic device having primary windings coupled in parallel and center-tapped secondary windings around a magnetic core. FIGS. 30 and 31 illustrate partially assembled perspective views of the magnetic device. The magnetic core of the magnetic device includes a first L-core segment LC1 and an opposing second L-core segment LC2. The first L-core segment LC1 includes a first leg LEG1 and a second leg LEG2 extending therefrom. The second L-core segment LC2 includes a first leg LEG1 and a second leg LEG2 extending therefrom. The first and second L-core segments LC1, LC2 may be designed with the flexibility as described above with respect to FIGS. 11 and 12.

The magnetic device includes a first primary winding PR1 coupled in parallel with a second primary winding PR2 with first and second and primary terminals p₁, p₂ for connection to another circuit element of a power converter or the like. Ends of the first and second primary windings PR1, PR2 are coupled together at the first and second primary terminals p₁, p₂. The first primary winding PR1 is formed around (e.g., wound around) the first leg LEG1 of the first L-core segment LC1 and the second primary winding PR2 is formed around (e.g., wound around) the first leg LEG1 of the second L-core segment LC2.

The magnetic device includes center-tapped secondary windings with a first secondary winding SC1 and a second secondary winding SC2 with first, second and third secondary terminals s₁, s₂, s₃ for connection to another circuit element of a power converter or the like. The center tap of the center-tapped secondary windings is coupled to the third secondary terminal s₃. The first secondary winding SC1 is formed around (e.g., stamped and formed sheet of metal placed around) the first leg LEG1 of the first L-core segment LC1 and the second secondary winding SC2 is formed around (e.g., stamped and formed sheet of metal placed around) the first leg LEG1 of the second L-core segment LC2. The first secondary winding SC1 is formed over the first primary winding PR1 around the first leg LEG1 of the first L-core segment LC1, and the second secondary winding SC2 is formed over the second primary winding PR2 around the first leg LEG1 of the second L-core segment LC2.

The primary windings PR1, PR2 may be dielectrically isolated from respective secondary windings SC1, SC2 by an insulating layer (e.g., tape or bobbin, not shown). Additionally, the primary windings PR1, PR2 and/or the secondary windings SC1, SC2 may be dielectrically isolated from the respective first and second L-core segments LC1, LC2 by an insulating layer (e.g., tape or bobbin, not shown). The magnetic device may also be encapsulated by a protective potting material such as epoxy individually or in combination with other circuit elements as part of a power converter or the like.

Thus, a magnetic device, a method of forming the same and a power converter have been introduced herein. In one embodiment, the magnetic device includes a first L-core segment including a first leg and a second leg extending therefrom. The magnetic device also includes an opposing second L-core segment including a first leg and a second leg extending therefrom. The magnetic device further includes a center-tapped secondary winding with a first secondary winding and a second secondary winding formed around at least one of the first leg and the second leg of the first L-core segment or the second L-core segment. In one embodiment, the second leg of the first L-core segment is substantially perpendicular to the first leg of the first L-core segment and the second leg of the second L-core segment is substantially perpendicular to the first leg of the second L-core segment. Additionally, a length of the first leg of the first L-core segment is elongated with respect to a length of the second leg of the first L-core segment and a length of the first leg of the second L-core segment is elongated with respect to a length of the second leg of the second L-core segment. Additionally, a thickness of the first leg and the second leg of the first L-core segment is substantially equal and a thickness of the first leg and the second leg of the second L-core segment is substantially equal.

In one embodiment, the first and second secondary windings are formed around the first leg of the second L-core segment. The magnetic device may also include a primary winding formed around at least one of the first leg and the second leg of the first L-core segment or the second L-core segment. In a related embodiment, the magnetic device may include a primary winding formed around the first leg of the second L-core segment, and the first and second secondary windings are formed over the primary winding around the first leg of the second L-core segment. The first and second secondary windings are stamped and formed sheets of metal. In another embodiment, the magnetic device includes a first primary winding formed around the first leg of the first L-core segment and a second primary winding formed around the first leg of the second L-core segment. In accordance therewith, the first secondary winding is formed over the first primary winding around the first leg of the first L-core segment and the second secondary winding is formed over the second primary winding around the first leg of the second L-core segment.

Turning now to FIGS. 32 to 35, illustrated are views of an embodiment of a magnetic device. FIGS. 32 and 33 illustrate a schematic view and a side view, respectively, of a magnetic device formed as an E-core magnetic device having primary windings coupled in series and secondary windings coupled in parallel around a magnetic core. FIGS. 34 and 35 illustrate partially assembled perspective views of the E-core magnetic device. The magnetic core of the E-core magnetic device includes a first core section including a first L-core segment LC11 and an opposing second L-core segment LC12. The first L-core segment LC11 includes a first leg LEG1 and a second leg LEG2 extending therefrom. The second L-core segment LC12 includes a first leg LEG1 and a second leg LEG2 extending therefrom. The magnetic core of the E-core magnetic device includes a second core section including a first L-core segment LC21 and an opposing second L-core segment LC22. The first L-core segment LC21 includes a first leg LEG1 and a second leg LEG2 extending therefrom. The second L-core segment LC22 includes a first leg LEG1 and a second leg LEG2 extending therefrom. In the illustrated embodiment, exterior surfaces EXS of the second leg LEG2 of the second L-core segments LC12, LC22 of the first and second core sections, respectively, are mated together (e.g., glued, adhesively secured or banded together). Also, end surfaces ES of the first leg LEG1 of the first L-core segments LC11, LC21 of the first and second core sections, respectively, are mated together (e.g., glued, adhesively secured or banded together). The first and second L-core segments LC11, LC12, LC21, LC22 may be designed with the flexibility as described above with respect to FIGS. 11 and 12.

The magnetic device includes a first primary winding PR1 coupled in series with a second primary winding PR2 with first, second and third primary terminals p₁, p₂, p₃ for connection to another circuit element of a power converter or the like. An end of the first and second primary windings PR1, PR2 are coupled together at the third primary terminal p₃. The first primary winding PR1 is formed around (e.g., wound around) the first leg LEG1 of the second L-core segment LC12 of the first core section and the second primary winding PR2 is formed around (e.g., wound around) the first leg LEG1 of the second L-core segment LC22 of the second core section.

The magnetic device includes a first secondary winding SC1 coupled in parallel with a second secondary winding SC2 with first and second secondary terminals s₁, s₂ for connection to another circuit element of a power converter or the like. An end of the first and second secondary windings SC1, SC2 are coupled together. The first secondary winding SC1 is formed around (e.g., stamped and formed sheet of metal placed around) the first leg LEG1 of the second L-core segment LC12 of the first core section and the second secondary winding SC2 is formed around (e.g., stamped and formed sheet of metal placed around) the first leg LEG1 of the second L-core segment LC22 of the second core section. The first secondary winding SC1 is formed over the first primary winding PR1 around the first leg LEG1 of the second L-core segment LC12 of the first core section, and the second secondary winding SC2 is formed over the second primary winding PR2 around the first leg LEG1 of the second L-core segment LC22 of the second core section.

The primary windings PR1, PR2 may be dielectrically isolated from respective secondary windings SC1, SC2 by an insulating layer (e.g., tape or bobbin, not shown). Additionally, the primary windings PR1, PR2 and/or the secondary windings SC1, SC2 may be dielectrically isolated from the respective second L-core segments LC12, LC22 by an insulating layer (e.g., tape or bobbin, not shown). The magnetic device may also be encapsulated by a protective potting material such as epoxy individually or in combination with other circuit elements as part of a power converter or the like.

Turning now to FIGS. 36 to 39, illustrated are views of an embodiment of a magnetic device. FIGS. 36 and 37 illustrate a schematic view and a side view, respectively, of a magnetic device formed as an E-core magnetic device having primary windings coupled in parallel and center-tapped secondary windings around a magnetic core. FIGS. 38 and 39 illustrate partially assembled perspective views of the E-core magnetic device. The magnetic core of the E-core magnetic device includes a first core section including a first L-core segment LC11 and an opposing second L-core segment LC12. The first L-core segment LC11 includes a first leg LEG1 and a second leg LEG2 extending therefrom. The second L-core segment LC12 includes a first leg LEG1 and a second leg LEG2 extending therefrom. The magnetic core of the E-core magnetic device includes a second core section including a first L-core segment LC21 and an opposing second L-core segment LC22. The first L-core segment LC21 includes a first leg LEG1 and a second leg LEG2 extending therefrom. The second L-core segment LC22 includes a first leg LEG1 and a second leg LEG2 extending therefrom. In the illustrated embodiment, exterior surfaces EXS of the first leg LEG1 of the second L-core segments LC12, LC22 of the first and second core sections, respectively, are mated together (e.g., glued, adhesively secured or banded together). Also, end surfaces ES of the second leg LEG2 of the first L-core segments LC11, LC21 of the first and second core sections, respectively, are mated together (e.g., glued, adhesively secured or banded together). The first and second L-core segments LC11, LC12, LC21, LC22 may be designed with the flexibility as described above with respect to FIGS. 11 and 12.

The magnetic device includes a first primary winding PR1 coupled in parallel with a second primary winding PR2 with first and second and primary terminals p₁, p₂ for connection to another circuit element of a power converter or the like. Ends of the first and second primary windings PR1, PR2 are coupled together at the first and second primary terminals p₁, p₂. The first primary winding PR1 is formed around (e.g., wound around) the first leg LEG1 of the first L-core segment LC11 of the first core section and the second primary winding PR2 is formed around (e.g., wound around) the first leg LEG1 of the first L-core segment LC21 of the second core section.

The magnetic device includes center-tapped secondary windings with a first secondary winding SC1 and a second secondary winding SC2 with first, second and third secondary terminals s₁, s₂, s₃ for connection to another circuit element of a power converter or the like. The center tap of the center-tapped secondary windings is coupled to the third secondary terminal s₃. The first secondary winding SC1 is formed around (e.g., stamped and formed sheet of metal placed around) the first leg LEG1 of the first L-core segment LC11 of the first core section and the second secondary winding SC2 is formed around (e.g., stamped and formed sheet of metal placed around) the first leg LEG1 of the first L-core segment LC21 of the second core section. The first secondary winding SC1 is formed over the first primary winding PR1 around the first leg LEG1 of the first L-core segment LC11 of the first core section, and the second secondary winding SC2 is formed over the second primary winding PR2 around the first leg LEG1 of the first L-core segment LC21 of the second core section.

The primary windings PR1, PR2 may be dielectrically isolated from respective secondary windings SC1, SC2 by an insulating layer (e.g., tape or bobbin, not shown). Additionally, the primary windings PR1, PR2 and/or the secondary windings SC1, SC2 may be dielectrically isolated from the respective first L-core segments LC11, LC21 by an insulating layer (e.g., tape or bobbin, not shown). The magnetic device may also be encapsulated by a protective potting material such as epoxy individually or in combination with other circuit elements as part of a power converter or the like.

Thus, a magnetic device, a method of forming the same and a power converter have been introduced herein. In one embodiment, the magnetic device includes a first core section having a first L-core segment including a first leg and a second leg extending therefrom, and an opposing second L-core segment including a first leg and a second leg extending therefrom. The magnetic device also includes a second core section having a first L-core segment including a first leg and a second leg extending therefrom, and an opposing second L-core segment including a first leg and a second leg extending therefrom. A surface of the second core section is mated (e.g., adhesively secured) to a surface of the first core section. In one embodiment, the second leg of the first L-core segment of the first core section is substantially perpendicular to the first leg of the first L-core segment of the first core section, and the second leg of the second L-core segment of the first core section is substantially perpendicular to the first leg of the second L-core segment of the first core section. Additionally, a length of the first leg of the first L-core segment of the first core section is elongated with respect to a length of the second leg of the first L-core segment of the first core section, and a length of the first leg of the second L-core segment of the first core section is elongated with respect to a length of the second leg of the second L-core segment of the first core section Additionally, a thickness of the first leg and the second leg of the first L-core segment of the first core section is substantially equal and a thickness of the first leg and the second leg of the second L-core segment of the first core section is substantially equal.

In one embodiment, a winding is formed around at least one of the first leg and the second leg of the first L-core segment or the second L-core segment of the first core section, and a winding is formed around at least one of the first leg and the second leg of the first L-core segment or the second L-core segment of the second core section. Regarding the mating of the first and second core sections, an end surface of the first leg of the first L-core segment of the first core section is mated to an end surface of the first leg of the first L-core segment of the second core section, and an exterior surface of the second leg of the second L-core segment of the first core section is mated to an exterior surface of the second leg of the second L-core segment of the second core section. Alternatively, an end surface of the second leg of the first L-core segment of the first core section is mated to an end surface of the second leg of the first L-core segment of the second core section, and an exterior surface of the first leg of the second L-core segment of the first core section is mated to an exterior surface of the first leg of the second L-core segment of the second core section.

In one embodiment, the magnetic device includes first and second primary windings formed around the first leg of the second L-core segment of the first and second core sections, respectively, and first and second secondary windings are formed around the first leg of the second L-core segment of the first and second core sections, respectively. Alternatively, the magnetic device includes first and second primary windings formed around the first leg of the first L-core segment of the first and second core sections, respectively, and first and second secondary windings are formed around the first leg of the first L-core segment of the first and second core sections, respectively.

Turning now to FIGS. 40 to 41, illustrated is a schematic view and a side view, respectively, of a magnetic device in the form of a coupled inductor. The magnetic core of the coupled inductor includes a first core section including a first L-core segment LC11 and an opposing second L-core segment LC12. The first L-core segment LC11 includes a first leg LEG1 and a second leg LEG2 extending therefrom. The second L-core segment LC12 includes a first leg LEG1 and a second leg LEG2 extending therefrom. The magnetic core of the coupled inductor includes a second core section including a first L-core segment LC21 and an opposing second L-core segment LC22. The first L-core segment LC21 includes a first leg LEG1 and a second leg LEG2 extending therefrom. The second L-core segment LC22 includes a first leg LEG1 and a second leg LEG2 extending therefrom. In the illustrated embodiment, exterior surfaces EXS of the second leg LEG2 of the second L-core segments LC12, LC22 of the first and second core sections, respectively, are mated together (e.g., glued, adhesively secured or banded together). Also, end surfaces ES of the first leg LEG1 of the first L-core segments LC11, LC21 of the first and second core sections, respectively, are mated together (e.g., glued, adhesively secured or banded together). The first and second L-core segments LC11, LC12, LC21, LC22 may be designed with the flexibility as described above with respect to FIGS. 11 and 12.

The magnetic device includes center-tapped secondary windings with a first secondary winding SC1 and a second secondary winding SC2 with first, second and third secondary terminals s₁, s₂, s₃ for connection to another circuit element of a power converter or the like. The center tap of the center-tapped secondary windings is coupled to an inductor winding IC and to the third secondary terminal s₃. The first secondary winding SC1 is formed around (e.g., stamped and formed sheet of metal placed around) the first leg LEG1 of the second L-core segment LC12 of the first core section and the second secondary winding SC2 is formed around (e.g., stamped and formed sheet of metal placed around) the first leg LEG1 of the second L-core segment LC22 of the second core section. The inductor winding IC is formed around the second leg LEG2 of the second L-core segments LC12, LC22 of the first core section and the second core section, respectively.

The secondary windings SC1, SC2 and/or the inductor winding IC may be dielectrically isolated from the respective second L-core segments LC12, LC22 by an insulating layer (e.g., tape or bobbin, not shown). The magnetic device may also be encapsulated by a protective potting material such as epoxy individually or in combination with other circuit elements as part of a power converter or the like. It should be noted that the coupled inductor including forming the secondary windings SC1, SC2 and/or the inductor winding IC about the first and second core sections may be assembled as described above.

Turning now to FIG. 42, illustrated is a side view of an embodiment of a magnetic core of a magnetic device in the form of a coupled inductor. The magnetic core of FIG. 42 is analogous to the magnetic core of FIG. 41 with the addition of gaps therein. A first gap (designated “a”) supports energy storage and a second gap (designated “b”) substantially prevents circulating magnetic flux. The first gap “a” may be created by grinding down the second leg LEG2 of the second L-core segments LC12, LC22 of the first and second core sections, respectively. The second gap “b” may be created by placing a spacer (partially shown and designated “s”) between the exterior surfaces EXS of the second leg LEG2 of the second L-core segments LC12, LC22 of the first and second core sections, respectively. The gaps “a”, “b” may be formed by, without limitation, air, a filler such as an epoxy or a spacer “s”. For ease of illustration, the second gap “b” is shown as partially filled with air or other filler (an upper portion thereof) and partially filled with the spacer “s”. Thus, the magnetic device includes at least one gap between a pair of adjacent legs therein. Of course, windings may be formed around the magnetic core of the coupled inductor as illustrated above.

Turning now to FIGS. 43 to 44, illustrated is a schematic view and a side view, respectively, of a magnetic device in the form of a coupled inductor. The magnetic core of the coupled inductor includes a first core section including a first L-core segment LC11 and an opposing second L-core segment LC12. The first L-core segment LC11 includes a first leg LEG1 and a second leg LEG2 extending therefrom. The second L-core segment LC12 includes a first leg LEG1 and a second leg LEG2 extending therefrom. The magnetic core of the coupled inductor includes a second core section including a first L-core segment LC21 and an opposing second L-core segment LC22. The first L-core segment LC21 includes a first leg LEG1 and a second leg LEG2 extending therefrom. The second L-core segment LC22 includes a first leg LEG1 and a second leg LEG2 extending therefrom. In the illustrated embodiment, exterior surfaces EXS of the first leg LEG1 of the second L-core segments LC12, LC22 of the first and second core sections, respectively, are mated together (e.g., glued, adhesively secured or banded together). Also, end surfaces ES of the second leg LEG2 of the first L-core segments LC11, LC21 of the first and second core sections, respectively, are mated together (e.g., glued, adhesively secured or banded together). The first and second L-core segments LC11, LC12, LC21, LC22 may be designed with the flexibility as described above with respect to FIGS. 11 and 12.

The magnetic device includes center-tapped secondary windings with a first secondary winding SC1 and a second secondary winding SC2 with first, second and third secondary terminals s₁, s₂, s₃ for connection to another circuit element of a power converter or the like. The center tap of the center-tapped secondary windings is coupled to an inductor winding IC and to the third secondary terminal s₃. The first secondary winding SC1 is formed around (e.g., stamped and formed sheet of metal placed around) the first leg LEG1 of the first L-core segment LC11 of the first core section and the second secondary winding SC2 is formed around (e.g., stamped and formed sheet of metal placed around) the first leg LEG1 of the first L-core segment LC21 of the second core section. The inductor winding IC is formed around the first leg LEG1 of the second L-core segments LC12, LC22 of the first core section and the second core section, respectively.

The secondary windings SC1, SC2 and/or the inductor winding IC may be dielectrically isolated from the respective first L-core segments LC11, LC21 and/or second L-core segments LC12, LC22 by an insulating layer (e.g., tape or bobbin, not shown). The magnetic device may also be encapsulated by a protective potting material such as epoxy individually or in combination with other circuit elements as part of a power converter or the like. It should be noted that the coupled inductor including forming the secondary windings SC1, SC2 and/or the inductor winding IC about the first and second core sections may be assembled as described above.

Turning now to FIG. 45, illustrated is a side view of an embodiment of a magnetic core of a magnetic device in the form of a coupled inductor. The magnetic core of FIG. 45 is analogous to the magnetic core of FIG. 44 with the addition of gaps therein. A first gap (designated “a”) supports energy storage and a second gap (designated “b”) substantially prevents circulating magnetic flux. The first gap “a” may be created by grinding down the first leg LEG1 of the second L-core segments LC12, LC22 of the first and second core sections, respectively. The second gap “b” may be created by placing a spacer (partially shown and designated “s”) between the exterior surfaces EXS of the first leg LEG1 of the second L-core segments LC12, LC22 of the first and second core sections, respectively. The gaps “a”, “b” may be formed by, without limitation, air, a filler such as an epoxy or a spacer “s”. For ease of illustration, the second gap “b” is shown as partially filled with air or other filler (an upper portion thereof) and partially filled with the spacer “s”. Thus, the magnetic device includes at least one gap between a pair of adjacent legs therein. Of course, windings may be formed around the magnetic core of the coupled inductor as illustrated above.

Thus, a magnetic device, a method of forming the same and a power converter have been introduced herein. In one embodiment, the magnetic device includes a magnetic core including a first core section and a second core section. The first core section includes a first L-core segment with a first leg and a second leg extending therefrom, and an opposing second L-core segment with a first leg and a second leg extending therefrom. The second core section includes a first L-core segment with a first leg and a second leg extending therefrom, and an opposing second L-core segment with a first leg and a second leg extending therefrom. A surface of the second core section is mated (e.g., adhesively secured) to a surface of the first core section. The magnetic device also includes a center-tapped secondary winding with a first secondary winding and a second secondary winding formed around at least one of the first leg and the second leg of the first L-core segment or the second L-core segment of the first core section or the second core section. The magnetic device also includes an inductor winding formed around at least one of the first leg and the second leg of the first L-core segment or the second L-core segment of the first core section or the second core section. The inductor winding is coupled to a center tap between the first secondary winding and the second secondary winding.

In one embodiment, the second leg of the first L-core segment of the first core section is substantially perpendicular to the first leg of the first L-core segment of the first core section, and the second leg of the second L-core segment of the first core section is substantially perpendicular to the first leg of the second L-core segment of the first core section. Also, a length of the first leg of the first L-core segment of the first core section is elongated with respect to a length of the second leg of the first L-core segment of the first core section, and a length of the first leg of the second L-core segment of the first core section is elongated with respect to a length of the second leg of the second L-core segment of the first core section. Additionally, a thickness of the first leg and the second leg of the first L-core segment of the first core section is substantially equal and a thickness of the first leg and the second leg of the second L-core segment of the first core section is substantially equal.

In one embodiment, the first secondary winding is formed around the first leg of the second L-core segment of the first core section, the second secondary winding is formed around the first leg of the second L-core segment of the second core section and the inductor winding is formed around the second leg of the second L-core segments of the first core section and the second core section. Alternatively, the first secondary winding is formed around the first leg of the first L-core segment of the first core section, the second secondary winding is formed around the first leg of the first L-core segment of the second core section and the inductor winding is formed around the first leg of the second L-core segments of the first core section and the second core section.

In one embodiment, an end surface of the first leg of the first L-core segment of the first core section is mated to an end surface of the first leg of the first L-core segment of the second core section, and an exterior surface of the second leg of the second L-core segment of the first core section is mated to an exterior surface of the second leg of the second L-core segment of the second core section. Alternatively, an end surface of the second leg of the first L-core segment of the first core section is mated to an end surface of the second leg of the first L-core segment of the second core section, and an exterior surface of the first leg of the second L-core segment of the first core section is mated to an exterior surface of the first leg of the second L-core segment of the second core section. Also, the magnetic device may include a gap between a pair of adjacent legs therein.

Turning now to FIGS. 46 to 47, illustrated is a schematic view and a side view, respectively, of a magnetic device in the form of an integrated magnetic device. The magnetic core of the integrated magnetic device includes a first core section including a first L-core segment LC11 and an opposing second L-core segment LC12. The first L-core segment LC11 includes a first leg LEG1 and a second leg LEG2 extending therefrom. The second L-core segment LC12 includes a first leg LEG1 and a second leg LEG2 extending therefrom. The magnetic core of the integrated magnetic device includes a second core section including a first L-core segment LC21 and an opposing second L-core segment LC22. The first L-core segment LC21 includes a first leg LEG1 and a second leg LEG2 extending therefrom. The second L-core segment LC22 includes a first leg LEG1 and a second leg LEG2 extending therefrom. In the illustrated embodiment, exterior surfaces EXS of the second leg LEG2 of the second L-core segments LC12, LC22 of the first and second core sections, respectively, are mated together (e.g., glued, adhesively secured or banded together). Also, end surfaces ES of the first leg LEG1 of the first L-core segments LC11, LC21 of the first and second core sections, respectively, are mated together (e.g., glued, adhesively secured or banded together). The first and second L-core segments LC11, LC12, LC21, LC22 may be designed with the flexibility as described above with respect to FIGS. 11 and 12.

The magnetic device includes a first primary winding PR1 coupled in series with a second primary winding PR2 with first, second and third primary terminals p₁, p₂, p₃ for connection to another circuit element of a power converter or the like. An end of the first and second primary windings PR1, PR2 are coupled together at the third primary terminal p₃. The first primary winding PR1 is formed around (e.g., wound around) the first leg LEG1 of the second L-core segment LC12 of the first core section and the second primary winding PR2 is formed around (e.g., wound around) the first leg LEG1 of the second L-core segment LC22 of the second core section.

The magnetic device includes center-tapped secondary windings with a first secondary winding SC1 and a second secondary winding SC2 with first, second and third secondary terminals s₁, s₂, s₃ for connection to another circuit element of a power converter or the like. The center tap of the center-tapped secondary windings is coupled to an inductor winding IC and to the third secondary terminal s₃. The first secondary winding SC1 is formed around (e.g., stamped and formed sheet of metal placed around) the first leg LEG1 of the second L-core segment LC12 of the first core section and the second secondary winding SC2 is formed around (e.g., stamped and formed sheet of metal placed around) the first leg LEG1 of the second L-core segment LC22 of the second core section. The inductor winding IC is formed around the second leg LEG2 of the second L-core segments LC12, LC22 of the first core section and the second core section, respectively.

The primary windings PR1, PR2 may be dielectrically isolated from respective secondary windings SC1, SC2 or the inductor winding IC by an insulating layer (e.g., tape or bobbin, not shown). Additionally, the primary windings PR1, PR2, and/or the secondary windings SC1, SC2 and/or the inductor winding IC may be dielectrically isolated from the respective second L-core segments LC12, LC22 by an insulating layer (e.g., tape or bobbin, not shown). The magnetic device may also be encapsulated by a protective potting material such as epoxy individually or in combination with other circuit elements as part of a power converter or the like. It should be noted that the integrated magnetic device including forming the primary windings PR1, PR2, the secondary windings SC1, SC2 and/or the inductor winding IC about the first and second core sections may be assembled as described above.

Turning now to FIGS. 48 to 49, illustrated is a schematic view and a side view, respectively, of a magnetic device in the form of an integrated magnetic device. The magnetic core of the integrated magnetic device includes a first core section including a first L-core segment LC11 and an opposing second L-core segment LC12. The first L-core segment LC11 includes a first leg LEG1 and a second leg LEG2 extending therefrom. The second L-core segment LC12 includes a first leg LEG1 and a second leg LEG2 extending therefrom. The magnetic core of the integrated magnetic device includes a second core section including a first L-core segment LC21 and an opposing second L-core segment LC22. The first L-core segment LC21 includes a first leg LEG1 and a second leg LEG2 extending therefrom. The second L-core segment LC22 includes a first leg LEG1 and a second leg LEG2 extending therefrom. In the illustrated embodiment, exterior surfaces EXS of the first leg LEG1 of the second L-core segments LC12, LC22 of the first and second core sections, respectively, are mated together (e.g., glued, adhesively secured or banded together). Also, end surfaces ES of the second leg LEG2 of the first L-core segments LC11, LC21 of the first and second core sections, respectively, are mated together (e.g., glued, adhesively secured or banded together). The first and second L-core segments LC11, LC12, LC21, LC22 may be designed with the flexibility as described above with respect to FIGS. 11 and 12.

The magnetic device includes a first primary winding PR1 coupled in series with a second primary winding PR2 with first, second and third primary terminals p₁, p₂, p₃ for connection to another circuit element of a power converter or the like. An end of the first and second primary windings PR1, PR2 are coupled together at the third primary terminal p₃. The first primary winding PR1 is formed around (e.g., wound around) the first leg LEG1 of the first L-core segment LC11 of the first core section and the second primary winding PR2 is formed around (e.g., wound around) the first leg LEG1 of the first L-core segment LC21 of the second core section.

The magnetic device includes center-tapped secondary windings with a first secondary winding SC1 and a second secondary winding SC2 with first, second and third secondary terminals s₁, s₂, s₃ for connection to another circuit element of a power converter or the like. The center tap of the center-tapped secondary windings is coupled to an inductor winding IC and to the third secondary terminal s₃. The first secondary winding SC1 is formed around (e.g., stamped and formed sheet of metal placed around) the first leg LEG1 of the first L-core segment LC11 of the first core section and the second secondary winding SC2 is formed around (e.g., stamped and formed sheet of metal placed around) the first leg LEG1 of the first L-core segment LC21 of the second core section. The inductor winding IC is formed around the first leg LEG1 of the second L-core segments LC12, LC22 of the first core section and the second core section, respectively.

The primary windings PR1, PR2 may be dielectrically isolated from respective secondary windings SC1, SC2 or the inductor winding IC by an insulating layer (e.g., tape or bobbin, not shown). Additionally, the primary windings PR1, PR2, and/or the secondary windings SC1, SC2 and/or the inductor winding IC may be dielectrically isolated from the respective first L-core segments LC11, LC21 and/or second L-core segments LC12, LC22 by an insulating layer (e.g., tape or bobbin, not shown). The magnetic device may also be encapsulated by a protective potting material such as epoxy individually or in combination with other circuit elements as part of a power converter or the like. It should be noted that the integrated magnetic device including forming the primary windings PR1, PR2, the secondary windings SC1, SC2 and/or the inductor winding IC about the first and second core sections may be assembled as described above.

Thus, a magnetic device, a method of forming the same and a power converter have been introduced herein. In one embodiment, the magnetic device includes a magnetic core including a first core section and a second core section. The first core section includes a first L-core segment with a first leg and a second leg extending therefrom, and an opposing second L-core segment with a first leg and a second leg extending therefrom. The second core section includes a first L-core segment with a first leg and a second leg extending therefrom, and an opposing second L-core segment with a first leg and a second leg extending therefrom. A surface of the second core section is mated (e.g., adhesively secured) to a surface of the first core section. The magnetic device includes a first primary winding and a second primary winding formed around at least one of the first leg and the second leg of the first L-core segment or the second L-core segment of the first core section or the second core section. The magnetic device also includes a center-tapped secondary winding with a first secondary winding and a second secondary winding formed around at least one of the first leg and the second leg of the first L-core segment or the second L-core segment of the first core section or the second core section. The magnetic device also includes an inductor winding formed around at least one of the first leg and the second leg of the first L-core segment or the second L-core segment of the first core section or the second core section. The inductor winding is coupled to a center tap between the first secondary winding and the second secondary winding.

In one embodiment, the second leg of the first L-core segment of the first core section is substantially perpendicular to the first leg of the first L-core segment of the first core section, and the second leg of the second L-core segment of the first core section is substantially perpendicular to the first leg of the second L-core segment of the first core section. Also, a length of the first leg of the first L-core segment of the first core section is elongated with respect to a length of the second leg of the first L-core segment of the first core section, and a length of the first leg of the second L-core segment of the first core section is elongated with respect to a length of the second leg of the second L-core segment of the first core section. Additionally, a thickness of the first leg and the second leg of the first L-core segment of the first core section is substantially equal and a thickness of the first leg and the second leg of the second L-core segment of the first core section is substantially equal.

In one embodiment, the first primary and secondary windings are formed around the first leg of the second L-core segment of the first core section, the second primary and secondary windings are formed around the first leg of the second L-core segment of the second core section, and the inductor winding is formed around the second leg of the second L-core segments of the first core section and the second core section. Alternatively, the first primary and secondary windings are formed around the first leg of the first L-core segment of the first core section, the second primary and secondary windings are formed around the first leg of the first L-core segment of the second core section, and the inductor winding is formed around the first leg of the second L-core segments of the first core section and the second core section. The first and second secondary windings may be stamped and formed sheets of metal.

In one embodiment, an end surface of the first leg of the first L-core segment of the first core section is mated to an end surface of the first leg of the first L-core segment of the second core section, and an exterior surface of the second leg of the second L-core segment of the first core section is mated to an exterior surface of the second leg of the second L-core segment of the second core section. Alternatively, an end surface of the second leg of the first L-core segment of the first core section is mated to an end surface of the second leg of the first L-core segment of the second core section, and an exterior surface of the first leg of the second L-core segment of the first core section is mated to an exterior surface of the first leg of the second L-core segment of the second core section.

The controller or related method as described above with respect to the power converters may be implemented as hardware (embodied in one or more chips including an integrated circuit such as an application specific integrated circuit), or may be implemented as software or firmware for execution by a processor (e.g., a digital signal processor) in accordance with memory. In particular, in the case of firmware or software, the exemplary embodiment can be provided as a computer program product including a computer readable medium embodying computer program code (i.e., software or firmware) thereon for execution by the processor.

Program or code segments making up the various embodiments may be stored in the computer readable medium. For instance, a computer program product including a program code stored in a computer readable medium (e.g., a non-transitory computer readable medium) may form various embodiments. The “computer readable medium” may include any medium that can store or transfer information. Examples of the computer readable medium include an electronic circuit, a semiconductor memory device, a read only memory (“ROM”), a flash memory, an erasable ROM (“EROM”), a floppy diskette, a compact disk (“CD”)-ROM, and the like.

Those skilled in the art should understand that the previously described embodiments of a power converter including an L-core segment and related methods of forming the same are submitted for illustrative purposes only. While a magnetic device has been described in the environment of a power converter, the magnetic device may also be applied to other systems such as, without limitation, a power amplifier and a motor controller.

For a better understanding of power converters, see “Modern DC-to-DC Power Switch-mode Power Converter Circuits,” by Rudolph P. Severns and Gordon Bloom, Van Nostrand Reinhold Company, New York, N.Y. (1985) and “Principles of Power Electronics,” by J. G. Kassakian, M. F. Schlecht and G. C. Verghese, Addison-Wesley (1991). The aforementioned references are incorporated herein by reference in their entirety.

Also, although the present invention and its advantages have been described in detail, it should be understood that various changes, substitutions and alterations can be made herein without departing from the spirit and scope of the invention as defined by the appended claims. For example, many of the processes discussed above can be implemented in different methodologies and replaced by other processes, or a combination thereof.

Moreover, the scope of the present application is not intended to be limited to the particular embodiments of the process, machine, manufacture, composition of matter, means, methods, and steps described in the specification. As one of ordinary skill in the art will readily appreciate from the disclosure of the present invention, processes, machines, manufacture, compositions of matter, means, methods, or steps, presently existing or later to be developed, that perform substantially the same function or achieve substantially the same result as the corresponding embodiments described herein may be utilized according to the present invention. Accordingly, the appended claims are intended to include within their scope such processes, machines, manufacture, compositions of matter, means, methods, or steps. 

What is claimed is:
 1. A magnetic device, comprising: a magnetic core, comprising: a first core section, comprising: a first L-core segment including a first leg and a second leg extending therefrom, and an opposing second L-core segment including a first leg and a second leg extending therefrom; a second core section, comprising: a first L-core segment including a first leg and a second leg extending therefrom, and an opposing second L-core segment including a first leg and a second leg extending therefrom, a surface of said second core section being mated to a surface of said first core section; a center-tapped secondary winding with a first secondary winding and a second secondary winding formed around at least one of said first leg and said second leg of said first L-core segment or said second L-core segment of said first core section or said second core section; and an inductor winding formed around at least one of said first leg and said second leg of said first L-core segment or said second L-core segment of said first core section or said second core section.
 2. The magnetic device as recited in claim 1 wherein said second leg of said first L-core segment of said first core section is substantially perpendicular to said first leg of said first L-core segment of said first core section, and said second leg of said second L-core segment of said first core section is substantially perpendicular to said first leg of said second L-core segment of said first core section.
 3. The magnetic device as recited in claim 1 wherein a length of said first leg of said first L-core segment of said first core section is elongated with respect to a length of said second leg of said first L-core segment of said first core section, and a length of said first leg of said second L-core segment of said first core section is elongated with respect to a length of said second leg of said second L-core segment of said first core section.
 4. The magnetic device as recited in claim 1 wherein a thickness of said first leg and said second leg of said first L-core segment of said first core section is substantially equal and a thickness of said first leg and said second leg of said second L-core segment of said first core section is substantially equal.
 5. The magnetic device as recited in claim 1 wherein said inductor winding is coupled to a center tap between said first secondary winding and said second secondary winding.
 6. The magnetic device as recited in claim 1 wherein said first secondary winding is formed around said first leg of said second L-core segment of said first core section, said second secondary winding is formed around said first leg of said second L-core segment of the second core section, and said inductor winding is formed around said second leg of said second L-core segments of said first core section and said second core section.
 7. The magnetic device as recited in claim 1 wherein said first secondary winding is formed around said first leg of said first L-core segment of said first core section, said second secondary winding is formed around said first leg of said first L-core segment of said second core section, and said inductor winding is formed around said first leg of said second L-core segments of said first core section and said second core section.
 8. The magnetic device as recited in claim 1 wherein an end surface of said first leg of said first L-core segment of said first core section is mated to an end surface of said first leg of said first L-core segment of said second core section, and an exterior surface of said second leg of said second L-core segment of said first core section is mated to an exterior surface of said second leg of said second L-core segment of said second core section.
 9. The magnetic device as recited in claim 1 wherein an end surface of said second leg of said first L-core segment of said first core section is mated to an end surface of said second leg of said first L-core segment of said second core section, and an exterior surface of said first leg of said second L-core segment of said first core section is mated to an exterior surface of said first leg of said second L-core segment of said second core section.
 10. The magnetic device as recited in claim 1 comprising a gap between a pair of adjacent legs.
 11. A power converter, comprising: a main switch coupled to an input of said power converter; a magnetic device coupled to said main switch, comprising: a magnetic core, comprising: a first core section, comprising: a first L-core segment including a first leg and a second leg extending therefrom, and an opposing second L-core segment including a first leg and a second leg extending therefrom; a second core section, comprising: a first L-core segment including a first leg and a second leg extending therefrom, and an opposing second L-core segment including a first leg and a second leg extending therefrom, a surface of said second core section being mated to a surface of said first core section; a center-tapped secondary winding with a first secondary winding and a second secondary winding formed around at least one of said first leg and said second leg of said first L-core segment or said second L-core segment of said first core section or said second core section; and an inductor winding formed around at least one of said first leg and said second leg of said first L-core segment or said second L-core segment of said first core section or said second core section; an auxiliary switch coupled to said magnetic device; and an output filter capacitor coupled to said auxiliary switch and an output of said power converter.
 12. The power converter as recited in claim 11 wherein said second leg of said first L-core segment of said first core section is substantially perpendicular to said first leg of said first L-core segment of said first core section, and said second leg of said second L-core segment of said first core section is substantially perpendicular to said first leg of said second L-core segment of said first core section.
 13. The power converter as recited in claim 11 wherein a length of said first leg of said first L-core segment of said first core section is elongated with respect to a length of said second leg of said first L-core segment of said first core section, and a length of said first leg of said second L-core segment of said first core section is elongated with respect to a length of said second leg of said second L-core segment of said first core section.
 14. The power converter as recited in claim 11 wherein a thickness of said first leg and said second leg of said first L-core segment of said first core section is substantially equal and a thickness of said first leg and said second leg of said second L-core segment of said first core section is substantially equal.
 15. The power converter as recited in claim 11 wherein said inductor winding is coupled to a center tap between said first secondary winding and said second secondary winding.
 16. The power converter as recited in claim 11 wherein said first secondary winding is formed around said first leg of said second L-core segment of said first core section, said second secondary winding is formed around said first leg of said second L-core segment of the second core section, and said inductor winding is formed around said second leg of said second L-core segments of said first core section and said second core section.
 17. The power converter as recited in claim 11 wherein said first secondary winding is formed around said first leg of said first L-core segment of said first core section, said second secondary winding is formed around said first leg of said first L-core segment of said second core section, and said inductor winding is formed around said first leg of said second L-core segments of said first core section and said second core section.
 18. The power converter as recited in claim 11 wherein an end surface of said first leg of said first L-core segment of said first core section is mated to an end surface of said first leg of said first L-core segment of said second core section, and an exterior surface of said second leg of said second L-core segment of said first core section is mated to an exterior surface of said second leg of said second L-core segment of said second core section.
 19. The power converter as recited in claim 11 wherein an end surface of said second leg of said first L-core segment of said first core section is mated to an end surface of said second leg of said first L-core segment of said second core section, and an exterior surface of said first leg of said second L-core segment of said first core section is mated to an exterior surface of said first leg of said second L-core segment of said second core section.
 20. The power converter as recited in claim 11 wherein said magnetic device comprises a gap between a pair of adjacent legs. 